A Multimedia Broadcast Multicast Service (MBMS) is multimedia broadcast and multicast service in a 3rd Generation Partnership Project (3GPP) wireless communication system. The MBMS service adopts a method for simultaneously transmitting data in multi-cell. The multi-cell transmit data in order to lower an error rate by combining a plurality of signals transmitted in different cells.
In case of Release-6 MEMS of 3GPP, data are transmitted from a plurality of cells. However, since a 3GPP Release-6 system is an asynchronous system, it cannot simultaneously receive the data transmitted from a terminal even if data are transmitted from a plurality of cells. Accordingly, there is a difficulty that the terminal should independently receive and combine signals transmitted from each cell. Although a plurality of errors occur due to a poor channel state, the terminal does not report the errors and data are not retransmitted. In order to lower the error rate, data repetition is performed in an application layer. The data transmission repetition is performed without feedback on a radio channel from the terminal. Accordingly, there is a problem in that data transmission repetition is performed while wasting radio resources even in a situation that data transmission repetition is not required.
In a 3GPP Long Term Evolution (LTE) MEMS service which is introduced after Release-6 and Release-7, when MBMS is serviced in the multi-cell, the cells transmit the same contents simultaneously.
In the multi-cell transmission, it is possible to lower the error rate by providing the terminal with reception signals of a higher strength than that of signals for a single cell. However, the low error rate is not provided to all the terminals within the entire coverage of the multi-cell. That is, it is difficult to expect the low error rate in case of terminals having a large cell radius and located in cell boundaries, and a terminal of a cell located in the boundary of multi-cell, not at the center of the multi-cell. On the other hand, it is easy to expect the low error rate in cells having a small radius and located at the center of the multi-cell. Therefore, when the radio channel environment is poor in the multi-cell transmission, a method for reducing a packet error rate is required. Accordingly, when an error occurs, it is required to retransmit the data.
The 3GPP Release-6 and Release-7 systems perform counting and recounting to check the existence of the terminal receiving the MEMS service. During counting and recounting procedures, the terminal hoping to receive MEMS service should response through Random Access Channel. In the Release-6 and 7 systems, a controlling radio network controller (C-RNC) controls interference caused by excessive random access between terminals by notifying probability information that the terminal should respond to the counting through the random access channel for counting and recounting.
The 3GPP LTE MBMS service performs polling, which is simpler than the counting and recounting in order to check whether there is a terminal receiving the MBMS data in the cell. However, there is a problem in that a polling procedure and a feedback channel for performing polling are not defined.